Abstract

Intense gigawatt relativistic electron beamgeneration studies were carried out in the presence of prepulse. Electron beams were generated using planar and annular graphitecathodes of various diameters at a fixed anode-cathode gap. For the planar cathode, the beam parameters obtained are , , and at a current density. With an annular cathode,, , and electron beam could be generated at a current density. The peak electric field in the diode varies from . A bipolar prepulse voltage has been recorded at the diode for both the cathodes. The amplitude of the negative prepulse voltage varies with the Marx generator voltage but the time duration remains same. The positive prepulse voltage varies both in amplitude and time duration with the Marx generator voltage. Some shot to shot variation in the diode voltage and current were recorded for the annular cathode due to the nonreproducibility of the prepulse generated plasma. It was found that the effect of prepulse is more pronounced in the cathode of larger diameter.